Heat exchanger in particular for an atmospheric cooling tower

ABSTRACT

A heat exchange comprises a battery of rectilinear tubes of synthetic plastic material connected at their respective ends to headers. At least one of the headers is fixed to the wall of the tower and the remainder of the exchanger is mounted by suspension members to allow free expansion of the tubes of the battery.

This application is a continuation, of application Ser. No 150,287,filed May 16, 1980 which is a division of application Ser. No. 893,788filed Apr. 5, 1978.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger for exchanging heatbetween a first fluid and at least a second fluid of the type comprisinga horizontal battery of long tubes which are supported at intervals byspacer devices. The first fluid circulates through the tubes and thesecond fluid flows about the battery of tubes transversely with respectto the tubes. The invention also relates to an atmospheric cooling towercomprising at least one heat excahnger of this type.

2. Description of the Prior Art

Atmospheric coolers, employed for cooling industrial waters by theatmosphere, may be of the "wet" type in which the water to be cooled isin direct contact with the air, or of the "dry" type in which the watertravels through tubes around which the air is circulated, or of the"combined" type which combines these two methods. In coolers of the"dry" type and "combined" type, there are generally employed exchangerscomprising finned or smooth metal tubes. In these two cases, fortechnical reasons, in particular internal and external corrosion of thetubes, and for economic reasons, there is a tendency to substitutesmooth tubes of plastic material for the metal tubes. However, theconstruction of such heat exchange batteries of smooth tubes of plasticmaterial presents delicate technical problems as synthetic materialshave high thermal coefficients of expansion. For example, a tube havinga length of around fifteen meters lengthens more than ten centimetersduring a temperature change of about 15°-20° C. to a temperature ofabout 90° C. Under these conditions, it will be understood that theinstallation of such batteries of tubes of synthetic material in acooler is very difficult, since the tubes will lengthen to this extentwhen the cooler changes from its operative to inoperative states. If noparticular precaution is taken, and these batteries of tubes of plasticmaterial are mounted in a manner identical to that of conventionalbatteries of finned metal tubes, the tubes, which are supported atintervals by spacer devices so as to maintain them perfectly rectilinearand parallel to each other, will deflect or bend between the spacerdevices and this will completely modify the geometry of the air passagesdefined between the tubes and considerably adversely affect the heatexchange capability of the battery. Further, when an installation isshut down during low outside temperature conditions, the tubes, inshrinking, exert very considerable forces on the support framework towhich the battery is fixed at each end.

SUMMARY OF THE INVENTION

An object of the invention is to overcome these drawbacks and to providea heat exchanger of the aforementioned type with means for absorbing thevariations in length of the tubes due to expansion and contraction.

According to the invention, there is provided a heat exchanger of theaforementioned type, wherein the tube battery is suspended, in at leasta part of its length, from a support structure by suspension members towhich said spacer devices are hooked.

According to a feature of the invention, in the case where the tubes ofthe battery are rectilinear and where the battery has, at its ends,inlet and outlet header means for said first fluid, the, for example,inlet means for the first fluid is rigidly mounted on the supportstructure and said battery is suspended freely in the remainder of itslength and at its other end.

According to a modification, in the case where the tube battery has acurvilinear contour and is mounted in a fixed manner on the supportstructure at each end, it is freely suspended between the two ends.

According to the invention, there is also provided an atmosphericcooling tower of the type comprising a chamber provided at its base withat least one air inlet, a heat exchange device for exchanging heatbetween a fluid and air disposed within the chamber, and means fordischarging the air in the upper part of the chamber, wherein the heatexchange device comprises at least one heat exchanger as definedhereinbefore.

BRIEF DESCRIPTION OF THE DRAWING

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawing whichis given solely by way of example and in which:

FIG. 1 is a longitudinal sectional view of a wet type atmospheric coolercomprising a heat exchanger having rectilinear tubes according to theinvention;

FIG. 2 is a partial view to an enlarged scale of the exchanger of thecooler of FIG. 1;

FIG. 3 is a view similar to FIG. 2 of a modification of the exchangeaccording to the invention;

FIG. 4 is an end elevational view of the exchanger of FIG. 3;

FIG. 5 is a view similar to FIG. 2 of another modification of theexchanger according to the invention;

FIG. 6 is a sectional view taken on line 6--6 of FIG. 5;

FIG. 7 is a diagrammatic cross-sectional view of a circular atmosphericcooler provided with a heat exchanger according to the invention;

FIG. 8 is a sectional view taken on line 8--8 of FIG. 7; and

FIG. 9 is a partial view of a spacer device for the heat exchanger ofFIGS. 7 and 8.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIG. 1, there is shown a forced-draught atmosphericcooler 1 comprising a chamber 2, the end walls 3 and 4 of which are openin their lower part thereby defining two air inlets 5, 6 and the upperwall 7 of which is provided with two openings 8 extended by sleeves 9 inwhich two suction fans 10 are mounted.

Disposed within the chamber 2 is a heat exchanger 11 comprising a seriesof tubes 7 extending throughout the length of the chamber 2. The heatexchanger 11 is surmounted by a system 12 of water distribution tubesprovided with dispersing nozzles 13 and by droplet separator panels 14suspended from longitudinal girders 15. Further, the cooler 1 has at itsbase a tray or pool 16 for receiving water coming from the distributionsystem 12 and by a circuit 17 for recycling water which is supplied tothe distributing system.

The heat exchanger 11 comprises a battery 18 of smooth tubes 7 ofsynthetic material, for example plastic material, these rectilinear andparallel tubes being fixed in a sealed manner at both ends in respectivewater boxes or headers 19, 20. The water box 19 comprises means 21, 22for connecting it to a water inlet pipe and a water discharge piperespectively.

In the embodiment shown in FIG. 2, the water box 19 includes partitionwalls 23 which divide it into three separate chambers 24, 25, 26 and theother water box 20 is divided by a median partition wall 27 into twoseparate chambers 28, 29. With this conventional arrangement, inoperation, the water effects four passages or travels four times throughthe length of the battery 18 by circulating through the four nests ofsuperimposed tubes 7 between the partition walls of the two water boxes,as shown by arrows in FIG. 2. As the tubes 7 are relatively flexible andof great length, they are supported at intervals by spacer devices 30,formed, for example as shown in FIG. 9, by rigid rectangular frames 31consisting of U-section members between which strips 32, provided withsemi-circular notches, define openings 33 therebetween for the passageand support of the tubes 7. A more detailed description of these spacerdevices may be had from U.S. patent application Ser. No. 760,690, filedJan. 19, 1977.

According to the invention, the battery 18 of tubes of the heatexchanger 11 is fixed to its support structure only at one of the endsthereof. In the illustrated embodiment, its water inlet and outlet box19 is fixed to the adjacent wall 3 of the cooler directly above the airinlet 5, for example by means of a plate 34 which is bolted or otherwisefixed to the water box 19 and to the wall 3. It is must be understoodthat the invention is not limited to this embodiment, and the water box19 or the like could be fixed by any other suitable means to a suitablefixed part of the cooler.

The battery of tubes 18 is freely suspended in the remainder of itslength and at its other end by suspension members 35 which are hooked tothe spacer devices 30 and to the water box 20 in their lower part and tothe longitudinal girders 15 in their upper part.

Associated with each spacer device 30 and with the water box 20 are twosuspension members 35 which are hooked to the respective sides of saidelements substantially in the middle of the height of the tube battery18. These suspension members 35 are disposed in two vertical planesoriented in the longitudinal direction of the battery 18. The upperhooking points of the suspension members 35 on the longitudinal girders15 are offset toward the suspended end of the battery 18 relative to thevertical from their lower hooking points 30' to the spacer devices 30,and to the water box 20 in respect to the end suspension member. Thus,the inclination of the suspension members 30 to the vertical permits anadjustment of the horizontal component of the weight of the suspendedelements. Moreover, there is added to this horizontal component theforce due to the bottom effect exerted against the bottom of the movingwater box, the resultant of these two forces enabling a sufficient pullto be exerted for tensioning the tubes 7 so that they are perfectlyrectilinear.

In the embodiment shown in FIG. 2, each pair of suspension members 35associated with a spacer device 30 is hooked in its upper part to a bar36 received in transversely-aligned notches of two racks 37 fixed to theupper part of these girders 15. In this way, the position of the upperhooking point of the suspension members, and consequently theinclination of the suspension members and the pull exerted on the tubes,may be adjusted. It must be understood that the invention is not limitedto this embodiment of the adjusting means and the latter may be of anyother suitable form. Appropriate means 38, for example, tensioning screwdevices, are provided for adjusting the length of the suspension members35 for the purpose of suitably positioning the battery of tubes so thethese tubes 7 are roughly horizontal in service.

The operation of the atmospheric cooler 1 is conventional and willconsequently only be described briefly. As mentioned before, the waterto be cooled arriving by way of the inlet pipe enters the upper part ofthe water box 19 and travels four times the length of the battery 18before issuing from the battery in the lower part of the water box 19.In the course of this circulation in the tubes 7 of the battery oftubes, the water is progressively cooled by air flow which, enters byway of the air inlets 5, 6, travels through the gaps between the tubes 7of the battery of tubes 18 and is then drawn out of the chamber 2 by thefans 10. In order to improve the transmission of heat from the wall oftubes 7 to the air, there is employed in the known manner a spray ofwater onto the external surfaces of the tubes. This spray of water iseffected by the distributing system 12 and the nozzles 13 and thesprayed water flow through the spaces between the tubes 7 of the battery18 and is received in the tray 16 then put back into circulation in thesystem 12 by the circuit 17 which includes a water pump 17'. Further,the droplet separator panels 14 mounted above the distributing system 12trap the droplets which are carried upwardly in suspension in the air.

As mentioned before, when the cooler 1 changes from its inoperativestate to its operative state, the tubes 7 pass from the ambienttemperature of the order of 10°-20° C. to a temperature of the order of80°-90° C. and the tubes of synthetic material undergo a considerablelengthening which may be ten to fifteen times greater than that of steeltubes of the same length. Such lengthening may exceed about tencentimeters in respect to tubes of about fifteen meters long. Owing tothe arrangement according to the invention, this expansion can occurfreely by swinging of the suspension members 35 about their upperhooking points. On the other hand, this would not be the case if, as inconventional constructions, the battery of tubes were fixed at bothends. Indeed, the tubes would then be prevented from free longitudinalexpansion and, instead of being maintained perfectly rectilinear theywould bend considerably between the intermediate spacer devices andbetween the water boxes and the adjacent spacer devices. Such expansionwould profoundly modify the geometry of the air passages between thetubes and would have considerable adverse effect on the uniformcirculation of the air through the tube battery and moreover wouldproduce an accumulation of the sprayed water at the lower points of thetubes and an absence thereof at the high points. In other words, goodthermal efficiency of the heat exchanger would be seriously affected.

Further, there is no problem at the sealed joints between the tubes andthe water boxes with the arrangement according to the invention. Thesuspension system is sufficient to exert a pull of between a fewhundredths of gram and a few kilograms on each tube to maintain it undertension.

The pulling force exerted on the tubes to maintain them rectilinear, maybe augmented by, for example a heavier or ballasted water box, springsor the like disposed between the suspended water box 20 and the fixedpart of the cooler, a pulley with a counterweight, etc.

A more detailed examination of the expansion problems which arise in abattery of smooth tubes of plastic material in which, as shown in FIG.2, the water to be cooled effects a plurality of passages, reveals thatthe temperature of the water and of the tubes of the first passage isdistinctly higher than that of the water and tubes of the last passage,that is to say the lower passage. Indeed, when the water reaches thelast passage, it has been cooled in the course of the precedingpassages, whereas in the first passage, the water arrives at asubstantially higher temperature and is in indirect contact with the airwhich has been heated by its passage through the three lower waterpassages. Consequently, there is differential expansion between thetubes of the different passages depending on their position in thebattery.

Thus, for example, in respect of a battery of 1.20 m in height having5,000 tubes 12 m long arranged for four passages as in the embodimentshown in FIG. 2, there is found a difference of linear expansion of 8 cmbetween the lowest tubes and the highest tubes of the battery for acooling difference of 50° C. Since the battery is fixed at only one end,this differential expansion of the tubes occurs freely. Thisdifferential expansion is shown in FIG. 2 in which the position of thewater box 20 is shown in dot-dash lines in its position when the heatexchanger is not in service and in full lines in its position when theexchanger is in operation.

In this respect, it will be noted that it is possible to take intoaccount the foreseeable expansion of the tubes and slightlyunder-dimension the upper tubes when assembling them so that, inservice, the water box 20 occupies exactly the required longitudinalposition in the air inlet 6 of the cooler. It will also be recognizedthat it is possible to adjust the position of water box 20, in thevertical direction, by the means 38 for adjusting the length of thesuspension members 35. In this way it is possible to adjust the assemblyso that, in operation, the tubes 7 are roughly horizontal therebyensuring a more uniform distribution of the sprayed water on the tubesand consequently better thermal efficiency of the system.

With reference now to FIGS. 3 and 4, there is shown a modification ofthe heat exchanger 11 in which the tube battery 39 does not have waterboxes at each end thereof. The tubes 7' of this battery are coiledto-and-fro and side-by-side in vertical planes extending in thelongitudinal direction of the battery and each thereof is connected atthe upper end to a fluid inlet header 40 for the inlet of the fluid tobe cooled. More precisely, there is provided a single coiled tube 7' ineach longitudinal vertical plane of the battery with the tubes of twoadjacent planes being vertically offset from each other. The advantageof this arrangement is the elimination of the relatively expensive waterboxes of conventional batteries and elimination of the many sealingjoints between the tubes and the water boxes, the cost of which isextremely high, in particular in respect to labor costs forinstallation.

FIGS. 5 and 6 show a modification of the exchanger of FIGS. 3 and 4 inwhich the tube battery 42 comprises a plurality of tubes 7" which arecoiled to-and-fro and disposed parallel to each other in eachlongitudinal vertical plane. This embodiment has the same advantagesover conventional tube batteries as that of FIGS. 3 and 4.

Reference will now be made to FIGS. 7 to 9 which show the inventionemployed in an atmospheric cooling tower 43 having a curvilinearcontour. The heat exchanger 11' is formed by a tube battery 44 of smoothtubes 7"' which are formed of synthetic material and of curvilinearconfiguration, for example in the shape of an arc of a circle, and areinterconnected at intervals by spacer devices 30 as describedhereinbefore. A description of a tube battery of this type and of thecooler in which it is mounted is given in U.S. Patent Application Ser.No. 760,690 to which reference may be made.

According to this invention, the problem of tube expansion andcontraction is solved by mounting the tube battery 44 in a fixed manneron the cooler only by its ends, that is to say its water boxes 45, 46,and suspending it freely throughout the remainder of its length. Thesuspension members 35 are preferably hooked to the upper part of thespacer devices 30 substantially in the middle of the width of thebattery 44 and they are each disposed in a vertical plane oriented inthe direction of the radius or curvature of the contour of the batteryin the region of the spacer device with which they are associated. Inorder to exert a continuous radial tension on the tubes, the upperhooking points of the suspension members 35 on the support structure ofthe tower, which may comprise for example a circular L-section beammember 47 fixed to the wall of the tower 43, are offset outwardly on theouter side of the contour of the tube battery 44 relative to thevertical from their lower hooking point on the spacer devices 30. Itwill be observed that this embodiment only requires the presence of asingle suspension member 35, FIG. 9, per spacer device 30. Of course,several suspension members 35 may be provided if necessary. Moreover, asfor the previously described rectilinear batteries, it is preferable toprovide means 38, FIG. 9, for adjusting the length of the suspensionmembers and means for adjusting the radial position of their upperhooking points so as to control the radial tension force to which thebattery is to be subjected. Such means may comprise elements such as 37,shown in FIG. 2 of the application.

Irrespective of the envisaged embodiment, the cooler having a suspendedbattery according to the invention has the advantage of requiring onlyvery simple mechanical means which present no working problem, even in adamp atmosphere such as is encountered in wet coolers of the type shownin FIG. 1 or in combined wet and dry coolers.

It will be understood that many modifications may be made in the variousembodiments described hereinbefore without departing from the scope ofthe invention. Thus, for example in the case of rectilinear batteries,the position of the hooking points of the suspension members on thespacer devices may be modified in accordance with particularrequirements of construction so as to place the hooking points eitherabove or below the horizontal plane containing the center of gravity ofthe battery instead of placing these points in this plane as illustratedin the drawings. The same is true in respect of the hooking point of theend suspension member of the suspended water box 20, it being moreoverpossible to longitudinally offset this point relative to the verticalfrom the centre of gravity of the water box. In the case of the tubebattery of curvilinear shape of FIGS. 7 to 9, the hooking points mayalso be different from that illustrated and indicated, it beingpossible, for example, to arrange the hooking points on the outer sideof the spacer device. Moreover, it must be understood that the heatexchanger according to the invention may be formed by a plurality ofrectilinear and/or curvilinear batteries disposed side-by-side orend-to-end at a sufficient distance from each other to allow the freeexpansion thereof.

Apart from the different modifications which may be made in thedescribed embodiments, it must be noted that the heat exchangeraccording to the invention is in no way limited to this application inan atmospheric cooling tower but, on the contrary, it may be employedwhenever a first fluid must be put in heat exchanging contact with atleast a second fluid and when there may be problems of the expansion ofthe tubes.

I claim:
 1. A heat exchanger for exchanging heat between a first fluid and at least a second fluid, of the type comprising a horizontal battery of tubes of substantial length supported at intervals by spacer devices, said first fluid circulating through said tubes and said second fluid passing through said battery transversely with respect to the tubes, wherein said battery is suspended in at least a part of its length from suspension members to which said spacer devices are suspended and including inlet and outlet means for the first fluid comprising an inlet collector and an outlet collector to which the respective ends of each of said tubes are connected, said tubes being coiled to-and-fro in vertical planes extending in the longitudinal direction of the battery, a rigid support structure, means connecting the inlet collector and the outlet collector to the rigid support structure, said suspension members including first hooking points on each of said spacer devices, means connecting the lower ends of the suspension members to the first hooking points, second hooking points for each of the suspension members, said second hooking points positioned above the first hooking points of the spacer devices and horizontally offset in a direction to continuously urge its connected spacer device and the tubes supported therein away from the rigid support structure to thereby maintain the horizontal path of said battery of tubes during expansion and contraction of the tubes thereof, and wherein at least some of said spacer devices are intermediate the ends of said battery and urged away from said rigid support structure by said suspension members and wherein each of said spacer devices comprises a rigid frame having openings for support and passage of said tubes.
 2. A heat exchanger as claimed in claim 1, comprising at least one tube coiled to-and-fro in each of said vertical planes and wherein two adjacent tubes are vertically offset from each other.
 3. A heat exchanger as claimed in claim 7, comprising a plurality of tubes coiled to-and-fro and disposed parallel to each other in each of said vertical planes.
 4. A heat exchanger for exchanging heat between a first fluid and at least a second fluid, of the type comprising a horizontal battery of tubes of substantial length supported at intervals by spacer devices, said first fluid circulating through said tubes and said second fluid passing through said battery transversely with respect to the tubes, wherein said battery is suspended in at least a part of its length from suspension members to which said spacer devices are suspended including means for directing the first fluid through said tubes, said means including a first water box and a second water box to which the tubes are connected in a sealed manner, a rigid support structure connected to the first water box, said suspension members including first hooking points on each of said spacer devices, means connecting the lower ends of the suspension members to the first hooking points, second hooking points for each of the suspension members, said second hooking points positioned above the first hooking points on the spacer devices and horizontally offset in a direction to continuously urge its connected spacer devices and the tubes supported therein away from the rigid support structure to thereby maintain the horizontal path of said battery of tubes during expansion and contraction of the tubes thereof, and wherein at least some of said spacer devices are intermediate the ends of said battery and urged away from said rigid support structure by said suspension members and wherein each of said spacer devices comprises a rigid frame having openings for support and passage of said tubes.
 5. A heat exchanger as claimed in claim 4 wherein said battery including the second water box is suspended freely along its length except at said first water box, further wherein said suspension members are oriented in the longitudinal direction of the battery, and wherein said upper hooking points are offset toward said second water box relative to the vertical from said lower hooking devices.
 6. A heat exchanger as claimed in claim 4 wherein, said battery has a curvilinear contour and is mounted in a fixed manner on a support structure at each of its ends, said first hooking points and second hooking points are horizontally offset in a direction to continuously urge its connected spacer device and the tubes supported therein radially away from the support structure to thereby maintain the curvilinear contour of said battery of tubes during expansion and contraction of the tubes thereof.
 7. A heat exchanger as claimed in claim 6, wherein each suspension member is disposed in a vertical plane oriented in the direction of the radius of curvature of said contour in the region of the associated spacer device.
 8. A heat exchanger as claimed in claim 6, wherein the support structure includes means for adjusting the radial position of the upper hooking point of the suspension members.
 9. A heat exchanger as claimed in claim 8, wherein said suspension members are hooked to the upper part of the spacer devices, substantially in the middle of the width of said battery. 